This application is based upon and claims priority of Japanese Patent Application No. 2001-342678, filed Nov. 8, 2001.
1. Field of the Invention
The present invention relates to a dinaphthopyrene compound which is suitably used in an organic EL element, an organic EL element using the dinaphthopyrene compound, and an organic EL display using the organic EL element.
2. Description of the Related Art
Organic EL elements have features such as self-lighting, high-speed response, and the like, and application thereof to flat panel displays is expected. Specifically, the EL elements in which a light emitting element having a large surface area which operates at 10V or less, is gathering people""s attention specifically after a two layered type. (laminated types) which laminates a positive hole transporting organic thin layer (positive hole transporting layer) and an electron transporting organic thin layer (electron transporting layer) laminated in two layers, have been reported (C. W. Tang and S. A. Van Slyke, Applied Physics Letters vol. 51, 913 (1987)). A laminated type organic EL element may have a basic structure of positive electrode/positive hole transporting layer/light emitting layer/electron transporting layer/negative electrode, and for the light emitting layer, a two layered types as mentioned earlier, the positive hole transporting layer or the electron transporting layer which functions on behalf of the light emitting layer may be used. In order to obtain an organic EL element having a high efficiency of light emission, the light emitting layer needs to have a high efficiency of light emission, and as such, the light emitting layer, excluding those which forms a layer using a single material, may include a type in which a small amount of high fluorescent light emitting pigment molecules are doped in the primary ingredient of a host material (C. W. Tang, S. A. Van Slyke, and C. H. Chen, Journal of Applied Physics vol. 65, 3610 (1989)).
However, with these organic EL elements, there is the problem that the color of the emitted light and the light-emitting efficiency are insufficient in actual use, and further improvements in actual use are required.
The present invention focuses on addressing these concerns, overcoming the aforementioned drawbacks of the prior art, and achieving the following object. Namely, an object of the present invention is to provide a dinaphthopyrene compound which has high color purity of green light and excellent light-emitting efficiency, light-emitting luminance and the like and which is suitable for an organic EL element, an organic EL element which uses the dinaphthopyrene compound and has high color purity of green light and excellent light-emitting efficiency, light-emitting luminance and the like, and an organic EL display which is high-performance and utilizes the organic EL element.
As a result of intensive studies carried out by the present inventors in order to overcome the above drawbacks, the present inventors discovered the following. Namely, specific dinaphthopyrene compounds have high color purity of green light and excellent light-emitting efficiency, light-emitting luminance and the like, and are particularly suited for organic EL elements which are used for emitting green light. An organic EL element and an organic EL display using this dinaphthopyrene compound have high color purity of green light and excellent light-emitting efficiency, light-emitting luminance and the like, and are high-performance, and can emit light at a higher luminance than conventional structures. Further, the dinaphthopyrene compound has excellent transportability of positive holes (carrier) or electrons. An organic EL element and an organic EL display which use the dinaphthopyrene compound in at least one of a positive hole transporting layer and an electron transporting layer have high color purity of green light and excellent light-emitting efficiency, light-emitting luminance and the like, are high-performance, and can emit light at a higher luminance than conventional structures.
The dinaphthopyrene compound of the present invention is a dinaphthopyrene compound comprising a structure expressed by the following structural formula 
where R1 through R18 may be the same or may be different to each other, and represent hydrogen atoms or substituents (excluding cases in which all are hydrogen atoms).
The organic EL element of the present invention is an organic EL element comprising an organic thin-film layer including a light-emitting layer in between a positive electrode and a negative electrode and the organic thin-film layer contains a dinaphthopyrene compound wherein the dinaphthopyrene compound comprising a structure expressed by the following structural formula 
where R1 through R18 may be the same or may be different to each other, and represent hydrogen atoms or substituents.
The organic EL display of the present invention uses the organic EL element of the present invention.